Passive identification, location and tracking of sound-emitting objects is generally performed by a system that includes an array of sensors used to detect acoustic waves produced by sound emitted from the object. Signals produced by the array of sensors in response to detection of the acoustic waves are determined in time and space. However, the information contained in these signals depends not only on the object emitting the sound but also on the number of sensors in the array and the geometry of the array.
A typical method for extracting location information from the signals obtained from the array is time difference of arrival (TDOA) whereby the difference between detection time of the acoustic wave at two sensors is exploited to determine the object's location. Successful application of TDOA has been limited to far field applications (i.e. when the object is assumed to be far enough away from the two sensors that acoustic waves can be assumed to be planar), with inaccuracies occurring in near field applications (i.e. distance to the object is less than ten times the distance between the sensors in the array and acoustic waves are spherical). The limited application of TDOA in near field situations has restricted locating sound-emitting objects due to difficulties in separating multiple sound emissions of the same object from multiple tracks of other objects. Identification of objects has been hindered by the high number of repeated measurements needed to characterize individual objects.